Apparatus for ore separation



March 8, 1960 Filed April 28. 1953 J. D. MALMQVIST ET AL APPARATUS FOR ORE SEPARATION 5 Sheets-Sheet l INVENTORS ATTORNEYS March 8, 1960 J. D. MALMQVIST ETAL 2,927,690

APPARATUS FOR ORE SEPARATION Filed April 28. 1953 5 Sheets-Sheet 2 INVENTORS -ATTORNEYS March 8, 1960 J. D. MALMQVIST ET AL 2,927,690

APPARATUS FOR ORE SEPARATION -5 Sheets-Sheet 3 Filed April 28. 1953 INVENTORS Jam/v DAV/0 M/lm V/sr 0 MR 60km 46m? 7710/4/15: MM MgM ATTORNEYS 5 Sheets-Sheet 4 INVENTORS ATTORNEYS March 8,1960 J. D. MALMQVIST ET AL APPARATUS FOR ORE SEPARATION Filed April 28. 1953 041 V -a V e? Jam/v 0 4140 MALMOV/ST "'0 W42 o'kA/v 46m? Mama/s ZQZW, %;M

March 8, 1960 J. D. MALMQVIST ET AL 2,927,690

APPARATUS FOR ORE SEPARATION Filed April 28. 1953 5 Sheets-Sheet 5 INVENTORS ATTORNEYS 2,927,690 APPARATUS FOR ORE SEPARATION Johan David Malrnqvist, Boliden, and Ivar Goran Ragnar Thomaeus, Saltsjo, Duvnas, Sweden, assignors to Bolidens Gruvaktiebolag, Skelleftehamn, Sweden, a joint-stock company of Sweden Application April 28, 1953, Serial No. 351,605 Claims priority, application Sweden May 15, 1946 3 Claims. (Cl. 20981) This is a continuation-in-part of our application Serial No. 746,968 of May 9, 1947, now abandoned.

This invention relates to and has for its object improvements in and relating to apparatus for ore separation.

In recovering metals from ores the so called picking method is being used in certain cases. According to this method the more or less finely crushed ore is separated in an earlier stage of the ore treatment into two or more qualities, only the richest of which being treated further. The usual hand picking from a picking band is, however, too expensive to be used widely. Further, in hand picking it is often difficult to separate rich ore parts from poor ones, if the ore minerals which are to be recovered are concealed in the gangue. The same difiiculty is at hand also in case attempts are made to pick-oil? automatically by optical methods, such as by using a photoelectric cell. The present invention involves a very cheap automatic separation of crushed ore and thus the invention is expected to be widely utilizable in many ore types. Due to its cheapness and superiority to optical methods the new method makes it possible to utilize in an economic way ores considerably more poor than ores which one hitherto has been able to utilize.

Apparatus have been proposed previously for automatic separation of metal bodies. In these cases, however, the problem only is to separate materials having variable electrical conductance only.

A satisfying and widely usable method for separating ores by automatic picking must be such to make it possible to separate minerals with high magnetic susceptibility from minerals with good electric conductance and also separate ores containing minerals with such properties from gangue.

In the apparatus according to the present invention ore in a more or less crushed state is caused to pass through an alternating magnetic field in a system of coils or solenoids with or without iron cores by means of a suitable conveyor device. The field will then be actuated by the different conductance or magnetic susceptibility of the minerals contained in the ore. The variation of the magnetic field thereby normally becomes greater the higher the concentration of ore minerals is in the passing goods of ore or metalliferous rock. By recording the changes of the magnetic field richer or poorer parts of the ore may be sorted. Thus the invention is based upon the principle of using an alternating magnetic field in order to record by means of said field richer or poorer ore parts, and in combination herewith an electric coupling adapted for the device with a mechanical separating device for automatically separating richer or poorer parts of the ore and separating ore parts with high magnetic susceptibility from ore parts with good electric conduc tance.

The apparatus for carrying out the method according to the invention into practice may be built in many different ways. Thus the ore may be caused to pass on a conveyor belt of rubber or any other suitable material.

ited tates Patent ice;

an ore part containing a greater percentage of ore: minerals moves into the field. The impedance will be higher than its normal value if an ore part with a high concentration of minerals with high magnetic suscepti-- bility is in the field and lower than its normal value if an ore part with a high concentration of minerals with:

good electrical conductance is in the field.

For a better understanding of the invention reference may be had to the accompanying diagrammatic drawings:- in which Figure 1 is a longitudinal view of an apparatus accord-- ing to the invention which is especially sensitive to variations of the ore concentration;

Figures 2 and 3 are a plan view and an elevational' view respectively diagrammatically showing a further em-- bodiment.

Figures 4 and 5 are diagrammatical longitudinal views: of the coil system and the conveyor belt showing two different ways to dispose the coils;

Figure 6 is a plan view of a part of the conveyor belt particularly showing means for sorting the ore into several compartments;

Figure 7 is a wiring diagram showing another form of the coil system; and

Figures 8A and 8B are two wiring diagrams showing other forms of a part of the coil system.

Referring to Fig. 1 of the drawings, 1 designates at transmitting coil connected to an alternating current source 2. The transmitting coil is placed above a con veyor belt 13 passing the ore beneath the separating apparatus. Two series connected receiving coils 3 and 4 of equal size are symmetrically disposed in relation to the transmitting coil.

In case the two receiving coils are differentially connected in series the sum of the induced electromotive force over the two coils is zero when no ore is present upon the conveyor belt. As soon, however, as ore parts containing minerals of a good electrical conductance or a high magnetic susceptibility are passing beneath the coil system, in the first case in coil 4 an alternating voltage is induced being lower than the one induced in coil 3 and in the latter case a higher alternating voltage is induced in coil 4 than in coil 3. In either case, however, an alternating voltage is obtained across the two coils connected in series. Two opposed rectifiers 3' and 4 are connected across coils 3 and 4, respectively. The voltage output from the coils 3 and 4 is applied to the input of the amplifier 5. Because the input impedance of the amplifier 5 is much greater than the forward impedance of the two rectifiers, half wave rectification of the alternating voltage induced in the coils 3 and 4 is obtained. Accordingly a pulsating direct voltage is developed across the rectifier 3 and a pulsating direct voltage is obtained across the rectifier 4 symmetrical with that across the rectifier 3 but in the opposite direction. A relatively higher positive direct voltage potential) is obtained at the output of coil 4 than at the one of coil 3 if ore containing minerals having good electrical conductance is passing, while the corresponding voltage will be negative relatively if ore containing minerals with high magnetic susceptibility is passing. Thus the arrangement is such that ore parts having high percentages of magnetic minerals will be separated from ore parts having high percentages of minerals with good electrical conductance.

By connecting the direct voltage from the coils 3 and 4 to grid and cathode respectively at the input of the amplifier 5 it will be possible to make the apparatus to cause the relay 6 for example to release, if the grid would obtain a higher negative voltage, i.e. when minerals with good electrical conductance actuate the system. The relay device switches on or off an electric motor 7 driven by current from the current source S. The motor drives, over the gears 9, a wheel 11 provided with a number of blades or shovels 10. The wheel 11, the axis of which is vertical, is rotated in bearings 12 and 12". As soon as the wheel has rotated a certain part of a revolution a blade will put aside upon the conveyor belt 13, which is driven by the wheels 14 and 14a, the ore part being present directly in the path of the moving blade. The arrangement is adjusted to cause the rotation of the wheel 11 to occur in connection with the presence beneath the coil system of an ore part of a relatively high concentration of minerals. The apparatus may also be adjusted in such a way that the ore part dressed is more or less rich of ore minerals of said properties. At the rotation movement the dressed part of the ore falls into the hopper 15, while the remaining product travels with the belt and falls into the hopper 16.

i It will, of course, be possible to change the release system for example by connecting the input of cathodegrid of the amplifier so as to cause the relay 6 to release, when an ore part with high concentration of minerals with high magnetic susceptibility is passing and in the same way to cause such a fraction to fall into the hopper 15. By arranging a further amplifier with relay and a further drive motor with rotating blades and hoppers three fractions may be separated, viz. I

V (1) One fraction rich in magnetic minerals;

(2) One fraction rich in minerals having good electrical conductance; and

(3) One fraction comprising the rest.

Another embodiment for accomplishing said object is shown in Figures 2 and 3, where elements similar or corresponding to elements shown in the embodiment of Figure l have obtained the same characters of reference. The ore to be concentrated is conveyed by a belt conveyer 13 of rubber or any other suitable material above which the transmitting coil 1 and the receiving coils 3 and 4 respectively are placed. Here again the forward resistance of the rectifiers 3 and 4' is much less than the resistance of resistor 39 so that half wave rectification is likewise obtained. In case no material passes on the belt conveyor beneath said coils or material containing only gangue with silicate minerals the voltage induced over the coils 3 and 4 are equal to each other so that no current will flow through the resistance 39. This means that there is no difference in voltage between cathodes and grids of the electronic tubes and 40' which are a part of a relay device for sensing the current direction through the resistance 39. The plate circuits of said tubes are each connected to circuits comprising electro-mechanical components forming a relay device. The variable resistance 3? is one example of the means used to adjust the output of the coils 3 and 4 to equal voltages under conditions of no material or material all gangue passing said coils.

In case material including ore parts containing minerals having high magnetic susceptibility should pass beneath the above-mentioned coils 1, 3 and 4, the voltage induced over the coil 4 will be higher than the one induced over the coil 3. Due to the rectifying arrangements 3', 4' a current will flow through the resistance 39. The grid of the electronic tube 40' will obtain a positive potential in relation to the cathode While the grid of .the electronic tube 40 will obtain a lower potential. The plate current of the tube 4d will then increase so much that the relay 6 connected in the plate circuit of the tube 4}) will operate and a contact of said rela connects the winding o the coil 3 to a vol o rc ca s n an i n c r (1 s shown) t be Pu led ink) ai o When s id i qn sat i ma ss in t Way .si e the rod 55' secured to said iron core will be caused to dis lass in d 6) le er whi h e atesvalve 33. When said valve is operated it admits com pressed air to actuate a piston working in the compressed air cylinder 32'. The shovel means 38 secured to the rod of said piston moves to feed the material laterally in relation to the belt conveyor beneath the receiving coil 4 down into the hopper 15.

In case material containing minerals having good electrical conductance is passed beneath the receiving coil 4 the current through the resistance 39 will flow in opposite direction and the relay of the circuit 6 will operate to cause the shovel means 38 to move the material laterally in the opposite direction to the movement of the material moved by the shovel means 38 mentioned above and down into the hopper 15'.

As will be understood the apparatus described is capable of separating three fractions viz.

( 1) The gangue being passed into the hopper 16,

(2) Magnetic material, being passed into the hopper (3) Material having high electrical conductance being passed into the hopper 15.

The coil system may, of course, be modified in several manners. It is, of course, not necessary to place the coil system above the conveyor belt, but it may be placed under it in the way shown by Figure 4. The receiving coils may also be placed side by side in different planes (Figure 5) or in the same plane. They may also be placed outside the transmitting coil.

According to the generic concept of this invention, as described and illustrated in the embodiments disclosed, the electromagnetic feeler comprises one (or several) transmitting coils and two (or several) compensated coils which are mutually compensated when no minerals are present in the vicinity of one of said coils. Rectifiers are connected to the two compensated coils, whereby a coupling is obtained which, as described above, makes it possible to separate magnetic minerals from minerals having good electrical conductance. It is quite evident that this combination of coils and rectifiers may be made in several ways. The rectifiers shown in Figure l are represented in as simple a way as possible. In order to obtain a better rectification each rectifier cell of Figure 1 may be substituted by a so called Gratz circuit as shown in Figure 7. The rectifier 3 is substituted by a Gratz circuit 22 and the rectifier 4 by another Gratz circuit 23. With these circuits full wave rectification of the alternating voltage induced in the coils 3 and 4 is obtained and more continuous direct voltage is thereby obtained. During each half cycle of the alternating voltage induced in the coil 4 direct current flows in the direct-ion of the arrow 25 while in a similar way the alternating voltage in the coil 3 will cause direct current to flow in the direction of the arrow 26. In case the two coils are completely compensated no current will flow through 24, which may be a relay sensitive to the direction of current for a resistance connected to the input of an amplifier. It will be understood that the direction of current in 24- Will depend on whether or not the alternating voltage induced into the coil 4 is higher than the one induced in the coil 3.

Other forms of practicable couplings are shown by Figures 8A and 8B.' In Figure 8A the'coils 3 and 4 are connected in series over a resistance 27 which on either side is provided with two opposed rectifiers 28 and 29. The resistance 27 is connected to the input of an amplifier. With this circuit only half wave rectification is obtained resulting in a pulsating direct voltage. The last mentioned coupling may be substituted by a Gratz circuit as shown in Figure 8B in which the Gratz circuit is substituted for the rectifier 28 and the circuit 31 for the rectifier 29. This circuit gives full wave rectification and a more continuous direct voltage. V

T he apparatus according to the principle of the invention may also be used for separating from the ore impurities of a certain such as scrap or waste iron or metal or the like, which for'some reason may have entered into the ore in the breaking or the crushing. Such a scrap iron or metal effects operation disturbances in the further crushing and it has formerly been necessary to remove them by hand to a large extent.

It is to be understood that various changes may be made in the apparatus described by those skilled in the art, without departing from the invention as defined by the claims.

Having now particularly described and ascertained the nature of our said invention and which mannerthe same is to be performed, we declared that what we claim is:

1. An apparatus for automatically separating from a non-homogeneous ore gangue parts having high magnetic permeability and parts having good electric conductance,

comprising a transmitting coil, means to pass a current varying with time through said transmitting coil to thereby create a varying magnetic field, two receiving coils difierentially connected in series, means to adjust the sum of the output voltages of said receiving coils to zero when said transmitting coil is transmitting under such impedance conditions where no ore is affecting the apparatus, a conveyor means to convey said ore within the magnetic field to thereby eflecta change in the impedance of said transmitting coil and to thereby unbalance said receiving coils, two rectifiers, one connected directly across each of said receiving coils, said rectifiers being connected in opposed series relation across a resistance element, a relay device, said resistance element forming the input to said device, said device being sensitive no to the direction of a current passing through said resistance element, and a mechanical ore separating means operatively connected to said relay device to separate ore particles having high magnetic permeability and ore particles having good electric conductance from the main part of the ore, wherein said transmitting and receiving coils are disposed on the same side of a plane through the ore conveying surface of said ore conveyor means.

2. An apparatus as defined in claim 1 further characterized in that the means to convey said ore is a conveyor belt that conveys said ore beneath said transmitting and receiving coils.

3. An apparatus as defined in claim 1 further characterized in that the means to convey Said ore is a con veyor belt that conveys said ore above said transmitting and receiving coils.

References Cited in the file of this patent UNITED STATES PATENTS 1,640,524 Augustine Aug. 30, 1927 2,057,835 Karajan et al. Oct. 20, 1936 2,154,156 Turner et al. Apr. 11, 1939 2,208,145 Zuschlog July 16, 1940 2,504,731 Rose et al. Apr. 18, 1950 2,587,686 Berry Mar. 4, 1952 FOREIGN PATENTS 284,307 Great Britain Ian. 29, 1929 

